I write for the same reason a toddler, at some occasion like a wedding party, dances.
The child hears the music and observes what the elders are doing. So he or she begins grinning and bouncing around.
I can remember the feeling I got when I read certain things, heard certain music. Alice in Wonderland, Charlie Parker, Ray Charles, Mozart, Ivanhoe, "Sailing to Byzantium," "To Elsie," "Howl," "At the Fishhouses." Movies like "The Searchers" or "His Girl Friday" or "Sullivan's Travels."
I remember the feeling those works gave me. I would like to give other people that feeling. (I am paraphrasing wise remarks I heard in an interview with the great saxophonist Dexter Gordon.)
I try to shape words into poetry, into works of art, because of the feeling I have gotten from great works of art. I'd like to create that feeling for someone else.
That's maybe a bit too simpleminded and practical. (Though honest.)